• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.201-204
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• 2001

In this paper, for modeling of electrical characteristics in Poly Silicon Thin Film Transistors with process parameters set up optimum values. So, the I-V characteristics of poly silicon TFT parameters are examined and simulated in terms of the variations in process parameter. And these results compared and analyzed simulation values with examination value. The simulation program for characteristic analysis used SUPREM IV for processing, Matlab for modeling by mathematics, and SPICE for electric characteristic of devices. Input parameter for simulation characteristics is like condition of device process sequence, these electric characteristic of I$_{D}$-V$_{D}$, I$_{D}$-V$_{G}$, variations of grain size. The Gate oxide thickness of poly silicon are showed similar results between real device characteristics and simulation characteristics.ristics.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.7
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• pp.2246-2256
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• 1996

To investigate the effect of material and precess variables on stamping formability of sheet materials, simulations for the cup drawing and the Yoshida buckling test were carried out using ABAQUS, commercial nonlinear finite element analysis code. The various factor effects on stamping formability of sheet materials were analyzed by the designed process according to Taguch's orthogonal array experiment. Cup drawing simulation showed that local neckling was very sensitive to plastic anisotropy parameter of sheet material and friction coefficient between sheet and tool interface. Simulations for the Yoshida buckling test have clarified that buckling behaviour of sheet material was mostly susceptible to yield stress and sheet thickness mostly. However, plastic anisotropy parameter and strain hardening coefficient affect moderately buckling behaviour of steel sheets after the buckling initiation.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.5
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• pp.49-54
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• 2004

In order to evaluate the stability of chatter vibration in turning precess, the micro-positioning cutting test with artificial tool vibration by piezoelectric actuation were carried out. In experiment, the phase lags between cutting forces and chip thickness variations were measured, and the dimensionless penetration-rate coefficient（$\overline{K^*}$） which is the most important parameter on the stability for chatter vibration was calculated. The results show that$\overline{K^*}$ can be applicable to the stability criterion for regenerative chatter vibration.

• Journal of the Korean Society for Precision Engineering
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• v.5 no.4
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• pp.24-31
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• 1988

The Upper Bound Solution has been used to investigate the effect of the various parameters on the floating-plug tube-drawing precess. A kinematically admissible velocity field considering the change of the tube thickness is proposed for the deformation process. Taking into account the position of the plug in the deforming region, shear energy at entrance and exit, friction energy on contact area, homogeneous energy are calculated. The theoretical values in proposed velocity field are good agreement with experimental values, It is investigated that the tube thickness in the deforming region is changed slightly toward minimization of deforming energy and then the drawing stress in lower than the crawing stress in the velocity field that the tube thickness is uniform.

• Journal of computational fluids engineering
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• v.21 no.1
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• pp.86-93
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• 2016

In this paper, heat transfer characteristics of pulsating heat pipes are investigated with the diameter and the number of tubes through the computational analysis of thermal flow. The numerical simulation includes the phase change precess with VOF model using OpenFOAM software. The numerical code is modified for the phase change to occur with saturation temperature. The numerical results are compared with the previous ones to validate the present code. The resonable results have been obtained based on the mass transfer time relaxation parameter considering the density ratio. When the ratio of length to diameter and the number of tubes are on the decrease, the thermal resistances also tends to decrease in the pulsating heat pipes. These numerical results will supply the base line data to design and to manufacture the pulsating heat pipe.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.30 no.1
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• pp.17-22
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• 2017

In this study, we designed the metallic reception part of a patch antenna using the phase field design method. The design object function is formulated with the S-parameter value which represent the return loss so that it is targeted to maximize radiation efficiency at a target frequency. The initial model of a patch antenna was designed via the ordinary theory based approach and its performance was enhanced by changing the structural configuration of the metallic part using the phase field design method combined with the double well potential functions. The final shape was proposed by removing the gray scale area along the structural boundary by employing a cut-off method. The proposed shape shows that the radiation efficiency at target frequency is significantly improved compared with the initial patch shape. The finite element analysis and optimization precess was performed using the commercial package COMSOL and Matlab programming.

• The Journal of Natural Sciences
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• v.8 no.1
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• pp.145-151
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• 1995

The stretching of synthetic fibers by hot dry process is very difficult, because these fibers have high glass transition temperature at above $150^{\circ}C$. But, we used a swell-wet stretching precess; the fibers are stretched in a swelling agent such as organic solvents at lower temperature. In this study, 100% acryl fibers were uniaxially stretched with free width at $70^{\circ}C$ by swell-wet process in organic solvents. The stretchability was estimated by stretching work. This work is concerned with stretching stress and strain, and initial modulus. We found that it is a good parameter for the estimatation of high strength to the acrylic fiber. The effects of stretching conditions on the molecular orientation for high strength and mechanical properties of PAN fibers were measured.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.8 no.2
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• pp.47-60
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• 1975

For the calculation of population parameter and estimation of recruitment of a fish population, an application of multiple regression method was used with some statistical inferences. Then, the differences between the calculated values and the true parameters were discussed. In addition, this method criticized by applying it to the statistical data of a population of bigeye tuna, Thunnus obesus of the Indian Ocean. The method was also applied to the available data of a population of Pacific saury, Cololabis saira, to estimate its recuitments. A stock at t year and t+1 year is, $N_{0,\;t+1}=N_{0,\;t}(1-m_t)-C_t+R_{t+1}$ where $N_0$ is the initial number of fish in a given year; C, number o: fish caught; R, number of recruitment; and M, rate of natural mortality. The foregoing equation is $$\phi_{t+1}=\frac{(1-\varrho^{-z}{t+1})Z_t}{(1-\varrho^{-z}t)Z_{t+1}}-\frac{1-\varrho^{-z}t+1}{Z_{t+1}}\phi_t-a'\frac{1-\varrho^{-z}t+1}{Z_{t+1}}C_t+a'\frac{1-\varrho^{-z}t+1}{Z_{t+1}}R_{t+1}......(1)$$ where $\phi$ is CPUE; a', CPUE $(\phi)$ to average stock $(\bar{N})$ in number; Z, total mortality coefficient; and M, natural mortality coefficient. In the equation (1) , the term $(1-\varrho^{-z}t+1)/Z_{t+1}$s almost constant to the variation of effort (X) there fore coefficients $\phi$ and $C_t$, can be calculated, when R is a constant, by applying the method of multiple regression, where $\phi_{t+1}$ is a dependent variable; $\phi_t$ and $C_t$ are independent variables. The values of Mand a' are calculated from the coefficients of $\phi_t$ and $C_t$; and total mortality coefficient (Z), where Z is a'X+M. By substituting M, a', $Z_t$, and $Z_{t+1}$ to the equation (1) recruitment $(R_{t+1})$ can be calculated. In this precess $\phi$ can be substituted by index of stock in number (N'). This operational procedures of the method of multiple regression can be applicable to the data which satisfy the above assumptions, even though the data were collected from any chosen year with similar recruitments, though it were not collected from the consecutive years. Under the condition of varying effort the data with such variation can be treated effectively by this method. The calculated values of M and a' include some deviation from the population parameters. Therefore, the estimated recruitment (R) is a relative value instead of all absolute one. This method of multiple regression is also applicable to the stock density and yield in weight instead of in number. For the data of the bigeye tuna of the Indian Ocean, the values of estimated recruitment (R) calculated from the parameter which is obtained by the present multiple regression method is proportional with an identical fluctuation pattern to the values of those derived from the parameters M and a', which were calculated by Suda (1970) for the same data. Estimated recruitments of Pacific saury of the eastern coast of Korea were calculated by the present multiple regression method. Not only spring recruitment $(1965\~1974)$ but also fall recruitment $(1964\~1973)$ was found to fluctuate in accordance with the fluctuations of stock densities (CPUE) of the same spring and fall, respectively.